Thanks for the reply, I see you've worked on two of them. It doesn't
say whether or not you managed to fix the one that is similar to my
case. I don't suppose you remember how it turned out?-it won't be 15
years ago, but it might be up to 13. :-|


N Cook wrote:
from my file
http://www.divdev.fsnet.co.uk/repair2.htm

Matrix SR 4000 auto chromatic guitar tuner, 1993?
Owner had connected an external 9V ps reversed
and knocked out the 78L05 as no reverse protection.
Replaced V Reg and cut trace to switch to put
a small 150mA diode in line
I was intrigued by another 3 pin TO92 device marked
8054
HN
3C31
Presumably working order - just wondered what it did.
Probably 8054HN not 8054 datecode , by Seiko,
activation voltage 3.8V to 4.2V, battery monitor.
One line is connected to INVERSE READ of the 80C51 micro
, I didn't trace any other lines.
Seems odd having this sophistication to hold
the micro from erroneous but not fatal operation
but no diode protection against battery or ext ps reversal,
especially in a product destined for musos.

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/